The devices are maintained in a database. In your Plex Data folder you should see a Plug-in Support folder, inside that folder is a Databases folder. Inside the database folder you will see several .db files. Obviously to continue Plex Media Server needs to be shutdown to ensure the database does not get corrupted. I also like to make a backup copy of the database myself in case something goes wrong.
You will need an application to open the SQLite database, I use DB Browser for SQLite. The database you are looking for is “com.plexapp.plugins.library.db”. Open this database file in the DB Browser for SQLite . Click the Browse Data tab and select the media_provider_resources table. You should see entries for all of the tuners that Plex sees. Select a tuner you want to delete and then click the Delete Record button. Repeat for the other two tuners you want to delete.
I will add that I find it odd that you have the same tuners duplicated. I have never seen Plex duplicate the same tuners. If the tuner matches with the uuid I have typically seen the uri get updated with the new IP Address of the tuner. Curious if these are actual tuners or virtual ones being emulated by some other software.
